Precursor ISI cancellation using adaptation of negative gain linear equalizer
An apparatus including a first circuit and a second circuit. The first circuit may be configured to generate an equalized signal in response to an input signal and an equalizer parameter signal. The equalizer parameter signal generally causes a cancellation of pre-cursor inter-symbol interference from a plurality of symbols in the input signal. The second circuit may be configured to generate (i) the equalizer parameter signal, (ii) a control signal and (iii) a data output signal in response to the equalized signal. The control signal generally causes an adjustment of the equalizer parameter signal. The adjustment of the equalizer parameter signal generally causes a decrease in the pre-cursor inter-symbol interference from the symbols.
1. An apparatus comprising:
a first circuit comprising a negative gain linear equalizer circuit, said first circuit configured to generate an equalized signal in response to an input signal and an equalizer parameter signal, said equalizer parameter signal causing a cancellation of pre-cursor inter-symbol interference from a plurality of symbols in said input signal; and
a second circuit configured to generate (i) said equalizer parameter signal, (ii) a control signal and (iii) a data output signal in response to said equalized signal, said control signal causing an adjustment of said equalizer parameter signal, said adjustment of said equalizer parameter signal causing a decrease in said pre-cursor inter-symbol interference from said symbols.
2. The apparatus according to claim 1 , wherein said second circuit comprises a Mueller-Muller baud-rate clock and data recovery circuit.
3. The apparatus according to claim 1 , wherein said second circuit comprises a Minimum Mean-Squared-Error baud-rate clock and data recovery circuit.
4. The apparatus according to claim 1 , wherein said second circuit further comprises an adaptive decision feedback equalizer.
5. The apparatus according to claim 4 , wherein (i) said adaptive decision feedback equalizer is further configured to generate a feedback signal in response to said data output signal and (ii) said second circuit is further configured to generate an intermediate signal by subtracting said feedback signal from said equalized signal.
6. The apparatus according to claim 5 , wherein (i) said second circuit further comprises a slicer configured to generate said output signal in response to said intermediate signal and (ii) said adjustment of said equalizer parameter signal causes sampling points to move toward a center of an eye opening at an input of said slicer.
7. An apparatus comprising:
a first circuit configured to generate an equalized signal in response to an input signal and an equalizer parameter signal, said equalizer parameter signal causing a cancellation of pre-cursor inter-symbol interference from a plurality of symbols in said input signal; and
a second circuit configured to generate (i) said equalizer parameter signal, (ii) a control signal and (iii) a data output signal in response to said equalized signal, said control signal causing an adjustment of said equalizer parameter signal, said adjustment of said equalizer parameter signal causing a decrease in said pre-cursor inter-symbol interference from said symbols, wherein said control signal comprises a target signal amplitude and said second circuit is further configured to generate an error signal in response to said equalized signal, said data output signal and said target signal amplitude.
8. The apparatus according to claim 7 , wherein said second circuit is further configured to generate said control signal in response to said error signal.
9. The apparatus according to claim 7 , wherein said second circuit is further configured to measure a rate of change in a phase of said equalized signal as said equalizer parameter signal changes.
10. The apparatus according to claim 7 , wherein said adjustment of said equalizer parameter signal comprises adaptation of a gain of said first circuit in response to said error signal and said data output signal.
11. The apparatus according to claim 10 , wherein said adaptation of said gain of said first circuit comprises multiplying samples of said error signal and samples of said data output signal according to an equation E(k)*D(k+1), where E(k) represents a sample of the error signal at a time k and D(k+1) represents a sample of the data output signal at a time k+1.
12. An apparatus comprising:
means for generating an equalized signal using a negative gain linear equalizer circuit, wherein said equalized signal is generated in response to an input signal and an equalizer parameter signal, said equalizer parameter signal causing a cancellation of pre-cursor inter-symbol interference from a plurality of symbols in said input signal; and
means for generating (i) said equalizer parameter signal, (ii) a control signal and (iii) a data output signal in response to said equalized signal, said control signal causing an adjustment of said equalizer parameter signal, said adjustment of said equalizer parameter signal causing a decrease in said pre-cursor inter-symbol interference from said symbols.
13. A method of symbol recovery in a receiver, comprising the steps of:
(A) generating an equalized signal in response to an input signal and an equalizer parameter signal, wherein said equalizer parameter signal causes cancellation of pre-cursor inter-symbol interference from a plurality of symbols in said input signal using a negative gain linear equalizer; and
(B) generating (i) said equalizer parameter signal, (ii) a control signal and (iii) a data output signal in response to said equalized signal, wherein said control signal causes an adjustment of said equalizer parameter signal, said adjustment of said equalizer parameter signal causing a decrease in said pre-cursor inter-symbol interference from said symbols.
14. The method according to claim 13 , further comprising performing one of Mueller-Muller baud-rate clock and data recovery and Minimum Mean-Squared-Error baud-rate clock and data recovery.
15. The method according to claim 14 , further comprising (i) generating a feedback signal in response to said data output signal using an adaptive decision feedback equalizer and (ii) generating an intermediate signal by subtracting said feedback signal from said equalized signal.
16. The method according to claim 15 ,
further comprising generating said output signal in response to said intermediate signal using a slicer, wherein said adjustment of said equalizer parameter signal causes sampling points to move toward a center of an eye opening at an input of said slicer.
17. The method according to claim 13 , further comprising generating an error signal in response to said equalized signal, said data output signal and said control signal, wherein said control signal is generated in response to said error signal.
18. The method according to claim 17 , further comprising adapting a gain of said linear equalizer in response to said error signal and said data output signal.
19. The method according to claim 18 , wherein adaptation of said gain of said linear equalizer comprises multiplying samples of said error signal and samples of said data output signal according to an equation E(k)*D(k+1), where E(k) represents a sample of the error signal at a time k and D(k+1) represents a sample of the data output signal at a time k+1.
20. The apparatus according to claim 1 , wherein said negative gain linear equalizer comprises an analog filter having a high frequency pole on an order of a data rate of said input signal.